The present invention relates, in general, to electrical transducers and, more particularly, to piezoresistive transducers.
Piezoresistive pressure sensors are in widespread use and typically have a transducer with a piezoresistive element disposed on a thin diaphragm, which flexes in response to pressure changes and thus causes a resistance change across the transducer. This resistance change is measured to determine the corresponding pressure acting on the sensor.
One particular prior sensor has a pressure sensor disposed on a thin diaphragm that has been formed from a silicon substrate. The resistive regions of the sensor are formed in the diaphragm region of the silicon substrate by diffusion to provide an electrical bridge. An electrical difference is sensed across this bridge to determine the pressure applied thereto. A problem with this prior sensor, however, is that the bridge requires lead-in taps which add some common resistance to each half of the bridge and to its differential sensing taps. This additional resistance lowers the sensitivity of the pressure sensor (i.e. reduces its span) and increases its susceptibility to mask misalignments. One adverse effect of such misalignment is an offset shift in the transducer's output. Accordingly, it is desirable to have a pressure sensor that has increased sensitivity and improved tolerance to slight mask misalignment during manufacture.